Conventional method of making silver nanowires is by solution process, and the nanowires are coated on the substrate by various coating methods (US Pub. No. 2011/0192633). The silver nanowire-based film made by the conventional method needs to go through post treatment or post annealing process in order to obtain an improved conductivity. Typical post treatment is by heating the film to an elevated temperature, e.g. between 100-150° C., such that the non-conductive material on the surface of the silver nanowires can be removed and the nanowires per se have a closer contact with each other. The first problem of using such a high temperature for the post treatment is the possibility of damaging the substrate of the films and the conductive area. Post treatment using high temperature also requires relatively longer time and higher cost. The method also requires subsequent material removal step by etching. High temperature also does not favor any patterning of the films. A refractive index-matching material used is normally needed, for example, when tin-doped indium oxide (ITO) is used as a substrate for the transparent conductive film, and after etching the film, a material having a refractive index matching the ITO is required in order to make the pattern invisible. Photosensitive materials in the ink for coating are degraded thermally under high temperature which damages the silver nanowire network, hence reduces the conductivity of the damaged area. When the damaged area is subject to UV light treatment, those photosensitive materials are further degraded in order to become less conductive. Silver nanowires, on the other hand, are not degraded under UV exposure and therefore become more conductive. Patterning using the conventional method by defining more conductive and less conductive areas results in a low optical property difference, hence it does not create invisible pattern in transparent conductive film.
In view of the foregoing problems, a new fabrication method for transparent conductive film with fewer process steps and favoring patterning of the film is demanded, especially in the manufacturing of touch panel and other displays with patterns.